In the semiconductor industry it is necessary to bond wafers together from different or even the same materials. For this purpose the wafers are normally first subjected to a cleaning stage with deionised water. After a drying stage following the cleaning stage the wafers are brought into contact with one another. The residual water molecules remaining after the drying stage ensure that the wafers already adhere to each other after they are brought into contact with each other, due to Van-der-Waals forces. After being brought into contact with each other, the wafers are introduced into an oven and heated at temperatures of up to 1000° C. or over. Due to the action of heat the wafers are bonded along the surfaces of contact to an atomic lattice which has a much greater bonding strength than the Van-der-Waals forces already acting at room temperature.
The disadvantage of the method of prior art is that the high temperatures generated may result in damage to the wafers, particularly if the wafers have already undergone different process stages. The high temperatures may, for example, result in the destruction of components located on the wafer.
In order to reduce the temperature required for bonding, attempts are already being made to pre-treat the wafer surfaces, for example by plasma activation, in order to achieve as high a bonding strength as in the conventional, temperature-intensive method even at temperatures of up to approximately 400° C.
The object of the invention is to propose a more economic method of bonding wafers and a device for bonding wafers, with which a sufficiently high bonding strength can be achieved.
This object is achieved according to the method with the features of claim 1 and according to the device with the features of claim 9. Advantageous embodiments of the invention are indicated in the independent claims.